The present invention relates to an ear microphone which converts a voice sound signal of its wearer into an electrical signal for transmission purposes. The voice sound signal is surfaced in his external auditory canal in the form of a bone-conducted vibration.
Although known ear microphones of this type are designed to be immune to air-conducted noise, they are nonetheless sensitive to vibrations conducted through their own structure including those caused by contact of the wearer's hair and finger tips with the projecting portions or lead wires outside the external auditory canal. Also strong wind blowing against the wearer's earflap introduces noise to the system. The vibrations caused by these factors are conducted by the microphone in the form of noise. Moreover, the noise level often exceeds the voice signal level to a degree that the voice sound signal transmission is marred.
In addition, such external vibrations are disproportionately emphasized in the high frequency portion of the speech range when converted into electrical signals. This is because the total communication system, including the ear microphone, is designed to compensate for the disproportionately high transmission loss in the high frequency range, which occurs during conduction of voice sound signals through the human skull and tissue from the voice cord to the external auditory canal. As a result, such external vibrations, when reproduced by a speaker at a receiving end, come out as high pitch noises.